1. Field of the Invention
The present invention relates to clamping two structures together, particularly two large, heavy structural elements, such as "I" beams and the like. More particularly, the present invention relates to a multi-element system for fastening a relatively temporary, heavy structure, such as for example a portable crane, to a basic support structure, such as for example the skid beams of an offshore oil rig or the support beams of a building construction site.
2. Prior Art
There is a need in the offshore oil rig industry to mount for operative use relatively large structures bearing great loads, such as for example a portable crane, onto the rig structure and particularly the rig's skid beams. The bottom structure of the portable crane usually includes two, fixed base girders which are rested on the support skid beams, perpendicular thereto, and in the prior art were welded to the skid beams after the crane had been properly located on the skid beams.
Such an operation would normally take a crew of four welders, three riggers or helpers, and a foreman five to ten hours to do the welding. Also, generally a welding crew is not available on the rig and must be brought in from the shore, a process which normally takes about twenty-four to thirty hours. Upon completion, the welding had to be ultra-sonicly tested for weld integrity. Additionally, while the welding operation was going on, the rig would be shut down. All of these factors have caused such a prior art operation to be very expensive. Finally, when it came time to relocate or remove the portable crane, it would take a crew one-half to three-quarters of the weld-up time to break the crane away from the skid beams.
In contrast, the clamping system of the present invention can be installed by two workers in approximately forty-five minutes and removed in a like period of time. Additionally, the clamping elements are relatively simple in structure and highly reliable, and can be built in practically any machine shop, and thus are relatively inexpensive.
Another exemplary, heavy load application to which the present invention is directed is in the building trade industry in setting up for example stiff leg, high rise cranes.
With respect to broadly clamping two, orthogonal, elongated items together, U.S. Pat. No. 3,591,214 to Gallay issued July 6, 1971 discloses a "Connection System for Steel Beams" which joins two "I" beams together by welding one of the joining elements to one beam and clamping the other end to the other beam with the use of bolted elements. The structure illustrated would not have the structural integrity or strength to withstand the loads that take place in the heavy structural art of the present invention. Additionally, welding is required, and relatively critical placement of the joining and clamping elements is necessary.
Two patents which disclose clamping structures for joining two orthogonal pipes or tubes in "C" shaped or "V" shaped seats are U.S. Pat. Nos. 2,088,890 (Winby et al issued Aug. 3, 1937) and 4,289,417 (Mandell issued Sept. 15, 1981).
Additional prior patents which may be of general background interest are listed below:
______________________________________ U.S. Pat. No. Patentee(s) Issue Date ______________________________________ 2,876,048 J. McCormick March 3, 1959 3,467,418 J. R. Redditt September 16, 1969 ______________________________________
3. General Discussion of the Invention
The present invention overcomes the relatively expensive and time consuming "welding" approach of the prior art with a straight-forward clamping system which includes four sets of two pairs of opposed clamping elements, which clamp together two, spaced, crane bearing beams to two, spaced, skid or support beams at four, spaced, end locations. Each related pair of clamping elements clamps one side of the flange of the upper, crane beam to the flange of the lower support beam, with the opposing, related pair clamp the other side of the upper flange to the lower flange.
Each pair straddles the lower, support beam flange and holds the lower flange in two opposed, horizontally disposed U-shaped areas and includes outboard, overlying plates which overlie the upper, crane beam flange. The clamping elements also have moveable gripping means, are actuated by threaded bolts which grip and lock the clamping elements to the two, opposed beam flanges of the crane and support beams, clamping the beams together.